[CIG-SHORT] Elastoplastic material question

[Eric Lindsey]

Yep, the models are converging. I don't think my solver is the best
(still need to figure that out), but in this case they are working to
the specified tolerance. When I decrease both the nonlinear/linear
tolerances by a power of 10, there is no change in the results either.

Lines from pylith's output just before the failure:

...
 -- Solving equations.
  0 SNES Function norm 8.855961010479e-05
  Linear solve converged due to CONVERGED_ATOL iterations 111
      Line search: Using full step: fnorm 8.855961010479e-05 gnorm
1.056268143324e-13
  1 SNES Function norm 1.056268143324e-13
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
 >> /home/class239/software/pylith/pylith-1.9.0-linux-x86_64/lib/python2.7/site-packages/pylith/problems/TimeDependent.py:200:run
 -- timedependent(info)
 -- Finishing advancing solution from t=3.15576e+07*s to t=6.31152e+07*s.
Fatal error. Calling MPI_Abort() to abort PyLith application.


Eric

On Mon, Nov 18, 2013 at 5:09 PM, Brad Aagaard <baagaard at usgs.gov> wrote:
> Eric,
>
> Have you verified convergence of the linear and nonlinear solvers up to the
> point you get an error? If the solver doesn't converge, you will get garbage
> that could show up as weird behavior.
>
> Brad
>
>
>
> On 11/18/2013 05:01 PM, Eric Lindsey wrote:
>>
>> I'm having trouble understanding the DruckerPragerPlaneStrain material.
>> I'm
>> using a simple homogeneous domain with no faults, and a simple Dirichlet
>> BC
>> imposing shear on the top/bottom. I've imposed an initial isotropic
>> compression, then I add the shear displacement gradually until it should
>> exceed the yield stress. On the sides I have a Neumann condition to
>> maintain the normal stress; for the moment I just set the shear tractions
>> to zero, but this value doesn't affect the results I'm getting. I expected
>> to see uniform plastic shear throughout the domain, but instead get the
>> message:
>>
>> RuntimeError: Infeasible stress state - cannot project back to yield
>> surface.
>>
>> If I include "allow_tensile_yield = True", the model runs, but instead of
>> homogeneous strain I'm getting the attached result. This is strange
>> because
>> at no point should the material be under absolute tension; the maximum
>> shear stress in the elastic case is never larger than the magnitude of
>> compressive stress. I think I am misunderstanding the setup of this
>> material somehow; hopefully it's a simple error? Input files are attached,
>> the elastic case works just fine. Any suggestions would be much
>> appreciated.
>>
>> Thanks,
>> Eric
>>
>> Relevant lines from the spatial databases:
>>
>>
>>
>> _______________________________________________
>> CIG-SHORT mailing list
>> CIG-SHORT at geodynamics.org
>> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short